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Thread: First Test - LSI indicates corrosive, does this matter?

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    First Test - LSI indicates corrosive, does this matter?

    I've been soaking up information for the past 6 months, and Thursday was the official go-live date for firing things up so time to put into practice what I've learned here. I think that I'm just looking for reassurance...?

    So I ran my first tests this weekend with the TF100 using a speed stir. My water is cold (47 degrees), and I just added salt on Saturday afternoon. Gas line hookup is tomorrow, so it should start warming up after that. Pool was filled with city water, and the pool company that shut it down and opened it up dumped some "things" in when they did it. I know one was polyquat. They said they added algaecide when they started it on Thursday too. I added bleach yesterday afternoon because my SQG won't run yet (water is too cold) - prior to that FC was at 0.

    Test sample was taken Sunday Evening - I did the FC and PH tests right away, and then let the water warm up to room temperature before doing the rest.

    FC 2.5
    CC 0.5
    PH 7.3
    TA 70
    CH 175
    CYA - not registering at all
    Salt - 4000

    The IntelliChem screen is a little scary. It shows that my water is corrosive (using LSI - I see the same thing when I look here and plug in my numbers: Pentair - Saturation Index Calculator). Do I have to worry about this?
    Intellichem.jpg

    Here's what I know (feel free to correct any of these if I'm wrong, I'm still learning here ):
    * When the water warms up (tomorrow if everything goes well with the gas line), the LSI will increase becoming less corrosive.
    * My PH will likely drift higher, also increasing LSI
    * I need to add CYA, probably to about 30 to give me the maximum CYA benefit and still allow for my intellichem ORP to maybe, possibly work...this will cause LSI to drop becoming more corrosive. This will put my FC target between 4-6 according to pool math.

    My intellichem manual says that for my vinyl pool I should have:
    TA: between 125 - 170
    CH: between 200 - 500

    Pool School Recommended levels say this:
    Vinyl with SWG
    TA 60-80
    CH 0-300 (Don't add)

    If you can't tell, I'm a little analytical. Just want to make sure that I have this right in my goal setting. I know that TFP recommendations differ from APSP, just trying to figure out if I need to worry about LSI. Going higher on TA and CH seems to increase LSI, but puts me outside of the TFP recommendations.
    • Since I have to run CYA a little lower trying to get the ORP to work, does this impact what I should be doing with anything else, like TA and CH? It seems that if I increase any of these my LSI increases making my water less corrosive...
    • I'm right in line with the Pool School Recommendations, do I even need to worry about LSI? I didn't know what it was until I read the word "corrosive" on my intellichem screen and started reading...and I'm worried about the equipment - from what I've read, corrosive is bad for gunite / concrete - not sure what effects it has on my pump / heater / swg, etc.
    Derek - November 2016 Build, Fill, Cover, and Close. Starting Equipment for the first time in Spring 2017: 26K IG 20x40 Vinyl, All Pentair: IntelliFlo VST 2, Clean and Clear 420 Cartridge Filter, EasyTouch 8, IntelliChem, IntelliChlor IC60 SWG, MasterTemp 250K NG Heater, GloBrite LED lights, Autelis Automation Integration, CoverStar Leading Edge Automatic Cover, Dolphin Quantum Robotic Cleaner, Interfab G-Force 2 slide, Interfab T7 diving board

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    Richard320's Avatar
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    Re: First Test - LSI indicates corrosive, does this matter?

    Short answer: no.

    Corrosive to plaster doesn't apply to a vinyl pool. Corrosive to the heater or pump is pretty much limited to pH. Keep the pH in range and the heat exchanger will be happy.

    Do be aware that a vinyl pool is still susceptible to Calcium scaling, so don't completely ignore the other end of the spectrum.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: First Test - LSI indicates corrosive, does this matter?

    Numbers look good. Let that pH drift up a little and as the water comes up to temp the CSI should look good.

    The heater is also very susceptible to scaling since it is a hot surface in contact with the water. Locally to the heat exchanger, the CSI will be higher. So you will just need to pay attention to any high CSI when you run the heater (based on time of year).

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    Patrick_B's Avatar
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    Re: First Test - LSI indicates corrosive, does this matter?

    High Chlorine is corrosive to Metallurgy in heaters, and heat pumps as well. Especially Copper alloyed metals.
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    Re: First Test - LSI indicates corrosive, does this matter?

    So I've been plugging along for about 10 days. Everything is holding. My TA increased slightly - either due to my first round of testing, or maybe the fact that I added a jug of liquid CYA, but at any rate, I now know after about half a dozen separate tests on separate days that I'm sitting here:
    FC: 3.5
    CC: 0.5
    PH: 7.3
    TA: 80
    CH: 150
    CYA: 0 < MyCYALevel < 20 (I've added stabilizer since my last test - sock is still in the skimmer. I can still see the dot, but just barely, with the water to the top. By the math with my pools volume from the dig diagram, and the volume of stabilizer that I added I should be right at 20.8)
    Salt: 3600 (although my SWG thinks that I have 2700 - I've tested multiple times with my Taylor Salt test and it's 3600)

    Two questions:
    1.) I've always had 0.5 CC (Chloramines) when I've tested. Do I need to worry about this, or is this normal?
    2.) Is it really necessary to test TA / CH in my vinyl pool on a regular basis? My pool is covered and has yet to have anyone step foot into it since it's still pretty cold up north. I can't see how these would change (although I'm pretty sure my liquid CYA caused TA to go up just a smidgeon).

    Thanks everyone for the help. I'm feeling confident at least in how I'm doing my testing. I've been consistent since my first results when I had an audience of my wife and my 4-year-old. I need my concentration time.
    Derek - November 2016 Build, Fill, Cover, and Close. Starting Equipment for the first time in Spring 2017: 26K IG 20x40 Vinyl, All Pentair: IntelliFlo VST 2, Clean and Clear 420 Cartridge Filter, EasyTouch 8, IntelliChem, IntelliChlor IC60 SWG, MasterTemp 250K NG Heater, GloBrite LED lights, Autelis Automation Integration, CoverStar Leading Edge Automatic Cover, Dolphin Quantum Robotic Cleaner, Interfab G-Force 2 slide, Interfab T7 diving board

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    Re: First Test - LSI indicates corrosive, does this matter?

    Quote Originally Posted by dw886 View Post
    TA: 80
    CH: 150

    Two questions:
    1.) I've always had 0.5 CC (Chloramines) when I've tested. Do I need to worry about this, or is this normal?
    2.) Is it really necessary to test TA / CH in my vinyl pool on a regular basis? My pool is covered and has yet to have anyone step foot into it since it's still pretty cold up north. I can't see how these would change (although I'm pretty sure my liquid CYA caused TA to go up just a smidgeon).
    I'll pass on your first question at the moment.

    For the TA & CH testing, you don't really need to test for them too often. Test TA a bit more than CH since you have a vinyl liner. TA is sensitive to how you operate the pool, so its good to keep an eye on it. CH isn't really important to a degree with vinyl. Unless you change significant amounts of water, it won't change much or fast over the season. Evaporation will leave the CH behind causing it to increase. Splash out and draining take CH with it. Your fill water (rain or the hose) will determine how fast and in what direction CH changes.

    Your change in in TA from 70 to 80 is within the accuracy/error of the test. Not saying you did anything wrong here. The accuracy of the test is plus or minus one drop when up to 10 drops of reagent are used, or plus or minus 10% of the final reading, when more than 10 drops of reagent are used.
    Also, CYA is acidic, so if any cause/effect, it would have caused TA to drop, not rise. I wouldn't be to concerned with 70 vs 80, its a non-issue.

    My 4 yr old likes to take the CYA mix bottle and squirt plain pool water into one of the larger test vials, refill the mix bottle and repeat. Also he likes to tell me when the pink turns to clear.

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    Re: First Test - LSI indicates corrosive, does this matter?

    Quote Originally Posted by Teald024 View Post
    I'll pass on your first question at the moment.

    For the TA & CH testing, you don't really need to test for them too often. Test TA a bit more than CH since you have a vinyl liner. TA is sensitive to how you operate the pool, so its good to keep an eye on it. CH isn't really important to a degree with vinyl. Unless you change significant amounts of water, it won't change much or fast over the season. Evaporation will leave the CH behind causing it to increase. Splash out and draining take CH with it. Your fill water (rain or the hose) will determine how fast and in what direction CH changes.

    Your change in in TA from 70 to 80 is within the accuracy/error of the test. Not saying you did anything wrong here. The accuracy of the test is plus or minus one drop when up to 10 drops of reagent are used, or plus or minus 10% of the final reading, when more than 10 drops of reagent are used.
    Also, CYA is acidic, so if any cause/effect, it would have caused TA to drop, not rise. I wouldn't be to concerned with 70 vs 80, its a non-issue.

    My 4 yr old likes to take the CYA mix bottle and squirt plain pool water into one of the larger test vials, refill the mix bottle and repeat. Also he likes to tell me when the pink turns to clear.

    Thanks Dave - that makes sense.

    Cold temp coupled with a pool that's been covered 24x7 seems to make for very little changes at this point. That'll likely change once it starts getting use.

    As for the CC number, do I have to worry about that, or is it normal to have some CC? The bottom of the pool had construction dirt in it when I opened two weeks back - most of it went to the filter. I cleaned the filters this past weekend once the pool water was clear - not sure if they needed it or not as my pressure hadn't changed, but after taking things apart they looked dirty and I wanted to try cleaning them just to understand the process.
    Derek - November 2016 Build, Fill, Cover, and Close. Starting Equipment for the first time in Spring 2017: 26K IG 20x40 Vinyl, All Pentair: IntelliFlo VST 2, Clean and Clear 420 Cartridge Filter, EasyTouch 8, IntelliChem, IntelliChlor IC60 SWG, MasterTemp 250K NG Heater, GloBrite LED lights, Autelis Automation Integration, CoverStar Leading Edge Automatic Cover, Dolphin Quantum Robotic Cleaner, Interfab G-Force 2 slide, Interfab T7 diving board

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    Richard320's Avatar
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    Re: First Test - LSI indicates corrosive, does this matter?

    We consider .5 CC or less to be the same as zero around here.

    Sometimes I'll have some for a few weeks and then it disappears again for a while. No rhyme or reason.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: First Test - LSI indicates corrosive, does this matter?

    Quote Originally Posted by Richard320 View Post
    We consider .5 CC or less to be the same as zero around here.

    Sometimes I'll have some for a few weeks and then it disappears again for a while. No rhyme or reason.
    Awesome, exactly what I was hoping to hear. I'm trying to avoid SLAMs and not start with them.

    Hopefully my reading over the last 6 months helps me to learn a little from others rather than having to stumble through some hurdles on my own. Right now, I'm fairly confident in the setup / testing - the reassurance of people here surely helps.

    My only apprehension is that I saw the PB dump in some "algaecides" in at close / open, and I'm more of a "read the label a few times over" type of person. I never got to see those labels, so I'm not entirely sure what was added. Hopefully not something that I regret down the road.
    Derek - November 2016 Build, Fill, Cover, and Close. Starting Equipment for the first time in Spring 2017: 26K IG 20x40 Vinyl, All Pentair: IntelliFlo VST 2, Clean and Clear 420 Cartridge Filter, EasyTouch 8, IntelliChem, IntelliChlor IC60 SWG, MasterTemp 250K NG Heater, GloBrite LED lights, Autelis Automation Integration, CoverStar Leading Edge Automatic Cover, Dolphin Quantum Robotic Cleaner, Interfab G-Force 2 slide, Interfab T7 diving board

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    Richard320's Avatar
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    Re: First Test - LSI indicates corrosive, does this matter?

    Quote Originally Posted by dw886 View Post
    Awesome, exactly what I was hoping to hear. I'm trying to avoid SLAMs and not start with them.

    Hopefully my reading over the last 6 months helps me to learn a little from others rather than having to stumble through some hurdles on my own. Right now, I'm fairly confident in the setup / testing - the reassurance of people here surely helps.

    My only apprehension is that I saw the PB dump in some "algaecides" in at close / open, and I'm more of a "read the label a few times over" type of person. I never got to see those labels, so I'm not entirely sure what was added. Hopefully not something that I regret down the road.
    The cheap algaecides break down with chlorine. Sometimes they cause foaming on the surface. The good ones break down too. The absolute worst is a copper-based algaecide that could lead to metal stains or green-haired children. You'll know if that's what they used.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: First Test - LSI indicates corrosive, does this matter?

    Quote Originally Posted by dw886 View Post

    My only apprehension is that I saw the PB dump in some "algaecides" in at close / open, and I'm more of a "read the label a few times over" type of person. I never got to see those labels, so I'm not entirely sure what was added. Hopefully not something that I regret down the road.
    Don't be apprehensive, jump in feet first. It's not magic and everything happens for a reason. Once you understand how to test, input readings into PoolMath and add chemicals, you find you only add exactly what you need.

    For the algicide info, call your pool builder and ask them what they used. You could always play dumb and say that you want to buy some more and wanted to know what kind it was.

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